Chelsea's late rush into the transfer market will see Samuel Eto'o join his former Anzhi Makhachkala team-mate Willian by moving to Stamford Bridge before the weekend, with the Cameroon forward expected to sign a 12-month deal.

Eto'o will cost around £5m as he becomes the latest departure from Anzhi, whose owner Suleyman Kerimov has withdrawn his lavish funding at the Dagestan club. The 32-year-old's representatives spent Wednesday in talks in London finalising a prospective move, with Chelsea determined to thwart his former club, Internazionale, and the Qatari side Al Gharafa to secure the striker's services. He is expected to undergo a medical on Thursday.

José Mourinho's pursuit of a player who excelled under his management at Inter – with whom they won the European Cup in 2010 – serves as confirmation that Chelsea have missed out on their principal summer target, Manchester United's Wayne Rooney, though the short-term nature of the Eto'o deal allows Chelsea the chance to pursue the Rooney option again if offered any encouragement.

Eto'o, a two-times Champions League winner who earned the equivalent of £300,000-a-week at Anzhi, will pick up around £4m at Stamford Bridge with reports in Russia suggesting Inter were offering considerably less to lure him back to Serie A.

He will also be reunited with Willian, whose £32m move from Anzhi was confirmed on Wednesday when the attacking midfielder was granted a work permit under the "exceptional talent rule" at a hearing in London. The 25-year-old forward has signed a five-year contract and will wear the No22 shirt at Chelsea.

"I'm very happy to be here, it's been a dream of mine to come and play here," the Brazilian said. "Chelsea are one of the best clubs in the world and now I'm going to play for one of the best managers in the world, so I'm very happy and looking forward to it."

The Europa League winners had trumped Tottenham Hotspur's bid for the player last week after the owner, Roman Abramovich, made a personal call to Kerimov to smooth the deal, albeit for a slightly higher price than that agreed with Spurs.

While that prompted a furious reaction at White Hart Lane – Willian had already undertaken a medical ahead of his proposed £30m transfer – Chelsea busied themselves preparing a case for Willian to be granted a permit under the "exceptional talent" clause as he is not a regular with Brazil. Mourinho supplied evidence on his behalf at the hearing with the panel duly convinced there is merit in the forward plying his trade in the Premier League.

Chelsea are also expected to spend around £3.5m to secure Porto's Ghana winger Christian Atsu, with the 21-year-old to be then loaned immediately to a European club to gain first-team experience.

His arrival, combined with that of Willian and Eto'o, will take Abramovich's spending beyond the £40m mark before Monday's 11pm closure of the transfer window, a proportion of which may be recouped if Victor Moses is permitted to depart.

Juan Mata will not be allowed to leave, with Chelsea insistent that the Spain international's future lies at Stamford Bridge despite Arsène Wenger's claim earlier this week that the playmaker was "on the market".

Mata, who is still working on gaining match fitness following a pre-season that started late after the Confederations Cup, has played a bit-part role under Mourinho and his father and agent, Juan Sr, was a guest in the Arsenal directors' box at Tuesday's Champions League qualifier against Fenerbahce.

But, while his chances have been limited to date, Chelsea are intent on retaining their two-times player of the year and will resist any interest expressed in his services before the deadline. Mata, too, is understood to be keen to remain at the club and regain his place in the first-team.